1. Technical Field of the Invention
The present invention relates to an end plate employed in a battery power source device used as a motor drive source or the like for an electrically powered automobile, and to a cooling device that cools this battery power source device by air cooling.
2. Description of Related Art
In a known type of battery power source of this kind, a large number of battery modules are constituted by being connected electrically and mechanically in series a row consisting of a plurality of single cells are arranged in parallel and held in a holder casing. High voltage power is extracted by connecting these battery modules electrically in series.
The present inventors developed a battery power source device wherein a large number of battery modules are arranged in parallel in a holder casing comprising a main casing body and two end plates, series with a electrical connection between the battery modules being achieved by holding ends of the battery modules in holding apertures provided in the end plates and locking the ends of the battery modules to a metal bus bar arranged on the outside face of the end plates.
However, with this prior example, since the end plates and bus bar were separate, there were the problems that deficiencies occurred in regard to the holding strength and rigidity of the battery modules and the operation of assembling the battery modules in the holder casing was complicated. There was also the problem of wrong insertion if the plus electrode and minus electrode of the battery modules were wrongly assembled in the holder casing and the problem of twisting between the single cells being produced on locking the battery modules to the bus bar.
Also, in a battery power source unit as described above, there was the serious problem of how to restrain the rise in temperature produced by evolution of heat from the battery modules tightly packed in the holder casing.
Furthermore, since nickel-hydrogen secondary cells were employed as the cells of a battery power source device of this type, and, under abnormal conditions, leakage of hydrogen from the cell cans may occur, safe measures for dealing with such hydrogen leakage posed a serious challenge.
Also, an arrangement is known in which high voltage power is supplied in an electrically powered automobile by mounting therein battery power source assemblies comprising a pair of battery power source devices electrically connected in series. However, in this case, efficient cooling of the battery power source devices presented a serious problem.
In order to suppress rising temperature brought about by evolution of heat from the batteries in the above battery power source device, the inventors modified the design of the holder casing and developed a cooling device having an air flow guide such as to make a suitable amount of cooling air flow along the battery modules.
However, with this prior example, not only was it difficult to suitably distribute the flow of air in regard to the battery modules but also it was difficult to effect uniform cooling between the single cells connected in series to constitute the individual battery modules. Specifically, the air flowing along the battery modules rises in temperature due to the heat received from the single cells whilst it is flowing from the upstream side to the downstream side, causing its cooling effect to gradually diminish. Thus it was extremely difficult to compensate for this by individually controlling the air flow rate and air flow speed for each individual battery module in order to achieve uniform cooling of the individual unit cells from the upstream side to the downstream side.